Splinter, often referred to as Master Splinter or Sensei by his students/sons, is a fictional character from Teenage Mutant Ninja Turtles comics and all related media. A mutant rat, he is the grave and stoic sage of the Turtles, their ninjutsu and martial arts instructor, and their adoptive father. The character was originally a parody of the Marvel Comics character Stick.

Teenage Mutant Ninja Turtles, commonly abbreviated as TMNT, is a media franchise created by the comic book artists Kevin Eastman and Peter Laird. It follows Leonardo, Donatello, Raphael and Michelangelo, four anthropomorphic turtle brothers trained in ninjutsu who fight evil in New York City. Supporting characters include the turtles' sensei, a rat called Splinter, their human friends April O'Neil and Casey Jones, and enemies such as Baxter Stockman, Krang, and their archenemy, the Shredder.